Process of recovering uranium from calutron wash solutions



`une 18, 1957 PROCESS OF' RECOVERING URANIUM FROM CALUTRON WASHSOLUTIONS Filed Feb. l2, 1945 R. Q- BOYER 9 Sheets-Sheet 1 June 18, 1957R. Q. BOYER 2,796,393

PROCESS OF' RECOVERING URANIUM FROM CALUTRON WASH SOLUTIONS Filed Feb.12, 1945 9 Sheets-Sheet 2 June 18, 1957 Filed Feb. 12,

R. Q. BOYER PROCESS OF RECOVERING URANIUM FROM CALUTRON WASH SOLUTIONSINVENTOR.

June 18, 1957 R. Q. BOYER 2,796,393

PROCESS OF RECOVERING URANIUM FROM CALUTRON WASH SOLUTIONS Filed Feb.12, 1945 9 Sheets-Sheet 4 SCRUBBED WASTE GASES APPARAWS June 18, 1957 R.Q. BOYER 2,796,393

PROCESS 0F RECOVERING URANIUM FROM cALUTRoN wAsR SOLUTIONS June 18, 1957R. Q. BOYER 2,796,393

PROCESS OF' RECOVERING URANIUM FROM CALUTRON WASH SOLUTIONS June 18,1957 R. Q. BOYER PROCESS OF RECOVERING URANIUM FROM CALUTRON WASHSOLUTIONS Filed Feb. l2. 1945 9 Sheets-Sheet 8' 9 Sheets-Sheet 9INVENTOR.

HUBERT 0. BOYER ATTORNEY.

BY v

June 18, 1957 R. Q. BoYER PROCESS OF RROOVERING URANIUM FROM OALUTRONwAsH SOLUTIONS Filed Feb. 12, 1945 (EN n: m

PROCESS F RECVERING URANIUM FROM CALUTRN WASH SLUTIONS Robert Q. Boyer,Berkeley, Calif., assigner to the United States of America asrepresented by the United States Atomic Energy Commission ApplicationFebruary 12, 1945, Serial No. 577,380

17 Ciainis. (Cl. 21M-1.5)

The present invention relates to processes of treating calutron washsolutions, and more particularly to plant processes of recoveringuranium from such wash solutions derived from calutrons employed in thecalutron method ot producing uranium enriched with U235.

In the copending application of Ernest O. Lawrence, Serial No. 557,784,tiled October 9, 1944 which issued as Patent No. 2,709,222 on May 24,1955, there is disclosed a calutron, a machine designed to separate theconstituent isotopes of an element and, more particularly, to increasethe proportion of a selected isotope in an element containing severalisotopes, in order to produce the element enriched with the selectedisotope, More specitically, the calutron mentioned is especiallydesigned to produce uranium enriched with the isotope U235.

ln the copending application of I ames M. Carter and Martin D. Kamen,Serial No. 532,159, tiled April 21, 1944 which issued as Patent No.2,758,006 on August 7, 1956, there is disclosed an improved process ofproducing uranium enriched with U235 employing the calutron method andcomprising first-stage and second-stage calutrons. In accordance withthis process, uranium of natural or normal isotopic composition istreated in a first-stage calutron in order to produce as a producturanium singly enriched with U235, which uranium singly enriched withU235 is treated in a second-stage calutron in order to produce as aproduct uranium doubly enriched with U235, which uranium doubly enrichedwith U235 may be used commercially. In the operation of either arst-stage calutron or a second-stage calutron the compound UCli istreated, whereby a residue of the UC14 is deposited on the parts of thecalutron disposed in the source region thereof, metallic uraniumenriched with U235 is deposited in the first pocket of the collector ofthe calutron, and metallic uranium improverished with respect to U235 isdeposited in the second pocket of the collector of the calutron. Thedeposit of UCl4 is recovered by a water wash step and the deposits ofmetallic uranium are separately recovered by acid wash steps; and thethree wash solutions are separately purified, if required, to producethree separate batches of a given compound of uranium. In this process,a rst batch of the uranium compound mentioned, produced from the waterwash derived from iirst-stage calutrons, is then converted back to UCl4for re-treatment in the first-stage calutrons, and a second batch of theuranium compoundmentioned, produced from the water wash derived fromsecond-stage calutrons, is then converted back to UC14 for re-treatmentin the second-stage calutrons.

In the copending application of Martin D. Kamen and Abel De Haan, SerialNo. 542,378, tiled June 27, 1944, now Patent No. 2,771,340, datedNovember 20, 1956, there is disclosed an improved process of purifying awater wash solution of the character mentioned in order to separateuranium from metallic impurities in the solution. In accordance withthis process, a water wash solution containing uranium, copper, nickel,iron, and

2,796,393 Patented .lune 18, 1957 chromium in the form of chlorides istirst concentrated; and the concentrated solution containing UO2++,Cu++,\ Nit-t, Fe+++, and Cr+++ ions is then reduced elecl trolytically,whereby the uranyl ion, UO2++, and the ferric ion, Fe+++, arerespectively reduced to the uranous ion, U++++, and the ferrous ion,Fe++. Thus, the re-vl duced solution contains U++++, Cu++, Ni++, Fe++,and Crtt+ ions; and to this reduced solution there is added oxalic acid,whereby the uranium is precipitated as U(C2Oi)2-6H2O away from the metalimpurities in the solution. The solution is then filtered in order toseparate the uranous oxalate precipitate, leaving the metal ionsmentioned in the tiltrate; and the uranium compound mentioned isconverted back to UCl4 for further treatment in the appropriate stage ofthe calutrons, as previously explained.

In plant operations employing the calutron method of producing uraniumenriched with U235, and utilizing the procedure disclosed in the Carterand Kamen application mentioned in the modified form disclosed in theKamen and De Haan application mentioned, all as explained above,considerable care must be exercised in handling the water wash solutionderived from the second-stage calutrons, in View of the fact that thelastrnentioned water wash solution constitutes ay chloride solution ofrelatively large volume and the uranium contained therein has beensingly enriched with U235 due to the previous treatment thereof in theiirst-stage calutrons. Moreover, after this water wash solution has beensubjected to oxalic acid treatment in order to precipitate most of theuranium as U(C2Oi)z6H2O away from the metal impurities contained and theprecipitate has been recovered by iiltration, a filtrate is recoveredcontaining a relatively small amount of uranium and substantially all ofthe metal impurities mentioned. Since the uranium contained in thelast-mentioned filtrate has been singly enriched with U235 due to theprevious treatment thereof in the iirst-stage calutrons, the salvage ofs'ubstantially all of this uranium from this ltr-ate is essential.Furthermore, in converting the U(C2O4)26H2O precipitate mentioned backto UCL; to be treated further, great care must be exercised, as nosubstantial loss of this valuable singly enriched uranium can betolerated.

Accordingly, it is an object of the invention to provide an improvedplant process of treating calutron wash solutions, especially suchsolutions derived from secondstage calutrons employed in the calutronmethod of producing uranium enriched with U235 wherein substantially allof the contained uranium is recovered and losses thereof to the outsideare negligible.

Another object of the invention is to provide an improved plant processof separating uranium from metal impurities contained in a calutron washsolution and then converting the recovered uranium back to uraniumtetrachloride for re-treatment in a calutron employed in the calutronmethod of producing uranium enriched with U235, wherein substantiallyall of the iiltrates, precipitates and other reaction products producedincident to the separation land conversion are subjected to appropriatesalvage treatments in order to prevent losses of the contained uraniumto the outside.

Another object of the invention is to provide an improved process ofdehydrating a uranous oxalate precipitate prior to calcination thereofto produce a uranium oxide.

A further object of the invention is to provide an improved iiltrationprocess utilizing a candle filter, where- -by uranous oxalateprecipitate may be loaded upon and subsequently unloaded from the candlefilter in an etiicient manner.

A further object v of the invention is to provide an improved process ofsalvaging relatively small amounts of uranous oxalate precipitatedeposited upon the surfaces o f filtering apparatus.

A further object of the invention is to provide an improved process ofdecomposing an oxalic acid solution containing a relatively small amountof uranium and of placing the contained uranium in solution in the plus6 oxidation state. Y

A further object of the inventionV is to provide an irnproved process ofsalvaging relatively smal] amounts of uranium contained in an oxalicacid filtrate from which uranous oxalate precipitate has been removed byfiltration.

A further object of the invention is to provide in conjunction with thetreatment in an electrolytic cell having 'a mercury cathode of asolution containing uranium and metal impurities, an improved process ofseparately recovering the uranium contained in the electrolyzed solutionand any uranium contained in the mercury of the mercury cathode.

A further object of the invention is to provide an improved process ofrecovering a fraction of uranium from 4reaction gases produced incidentto the calcination of uranous oxalate.

A further object of the invention is to provide an improved process ofrecovering a fraction of uranium from Areaction gases produced incidentto the conversion of a uranium oxide to uranium tetrachloride.

A still further object of the invention is to provide in conjunctionwith the reclamation of vuranium from solution an improved processofpreventing re-oxidation of U++++ ion back to UO2++ ion, followingreduction of UO2++ ion to U++++ ion.

The invention, both asto its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following speciication, ltaken inconnection with the accompanying drawin-g in which Figures l to 8,inclusive, taken together, illustrate diagrammatically a plantarrangement for treating calutron wash solutions, and in which theprocesses of the present invention may be carried out. In order Ito forma unied plant arrangement of the drawing, Figs. 1 to 4, inclusive,should be arranged in upstanding position in sequence to the right toform a first strip; Figs. 5 to 8, inclusive, should be arranged inupstanding position in sequence to the right to form a second strip; andthe Iirst strip should be placed abovethe second strip to form a blockas shown in reducedscale in Fig. 9 of the drawing.

Referring now more particularly to Figs. l to 8, inclusive, of thedrawing, there is illustrated diagrammatically a plant arrangement fortreating calutron wash solutions that embodies the features of thepresent invenvtion and comprises a storage tank 501 adapted to receive acalutron wash solution which is to be subjected to treatment. Moreparticularly, the wash solution contained in the storage tank 501normally comprises a mixture of the Water wash solution derived fromwashing the deposits of UC14= residues from the parts disposed in thesource regions ofthe second-stage calutrons and the acid wash solutionderived from washing the deposits of metallic uranium enriched with U235from the rst pockets of the collectors of the iirst-stage calutrons;this wash solution comprising a chloride solution containing' thefollowing ions: UOz++, U++++, Fe+++, FeJfi', C'u++, Cr+++, and Ni++; theuranium contained being singly enriched with the isotope U235 withrespect to natural or normal uranium and the Venrichment factor beingvof the order of 20; al1 as disclosed in the previously mentionedapplication of Carter and Kamen. Y Y

source of H2O2, not shown, whereby Vthe wash solution contained in theoxidation tank 502 may be subjected to oxidation in order to oxidize theU++++ and Fe++ ions respectively to UO2++ and Fe+++ ions, the oxidizedsolution constituting a dilute HCl solution containing UO2++, Further,the oxidation tank 502 is connected to a first-stage evaporator unit101, whereby the oxidized solution mentioned may be delivered from theoxidation tank 502 to the evaporator unit 101 to be lconcentrated byevaporation. The evaporator unit 101 is connected to a storage tank 102,which in turn is connected to a second-stage evaporator unit 103,whereby the solution concentrated in the firststate evaporator unit 101may be delivered to the storage tank 102 and then delivered therefrom tothe secondstage evaporator unit 103 to be further concentrated byevaporation.

The storage tank 501 is connected to an oxidation tank Y Preferably, therst-stage evaporator unit 101 and the second-stage evaporator unit 103are substantially identical, although the evaporator unit 101 normallyhas a slightly larger heat-exchange capacity than the evaporator unit103, in view of the fact that a larger amount of vapor is driven fromthe solution entering the first-stage r evaporator unit 101 than isdriven from the solution entering the second-stage evaporator unit 103,as explained more fully hereinafter. Also, it is preferable that each ofthe evaporator units 101 and 103 is substantially identical to theevaporator unit disclosed in `the copending application of Robert Q.Boyer, Serial No. 529,012, led March 31, 1944 which was abandoned onMarch 14, 1951.

Speciiically, the evaporator unit 101 comprises a header 104,A amanually adjustable inlet valve 105, a manually adjustable outlet valve106, an evaporator 107, a deentrainment head 108, and a -condenser 109.The header 104, the evaporator 107, and the de-entrainment head 108 arelined with tantalum; the evaporator 107 is connected to a suitablesource of steam under pressure, not shown; and the condenser 109 issupplied with cooling water from a source, not shown. Similarly, theevaporator unit 103 comprises a header 110, a manually adjustable inletvalve 111, a manually adjustable outlet valve 112, an evaporator 113, ade-entrainrnent head 114, and a condenser 115. The header 110, theevaporator 113, and thev de-entrainment head 114 are lined withtantalum; the evaporator 113 is connected to a suitable source of steamunder pressure, not shown; and the condenser 115 isY supplied withcooling water from a source, not shown. The condensers 109 and 115 areconnected in parallel to a storage tank 501e, whereby the vapor enteringthe vcondensers 109 and 115 from the de-entrainment heads 108 and 114 ofthe evaporator units 101 and 103, respectively, is condensed and thecondensate is drained into the storage tank 501a. TheV condensatecontained in the storage tank 501a is composed principally of H2O,although it does contain a small amount of HC1 and traces of uranium andmetal impurities. In view of the fact that this condensate contained inthe storage tank 501a does contain a trace of uranium singly enrichedwith U235 with respect to natural or normal uranium, it is importantthat none of it bey lost to the outside. In order to achieve this end,the condensate contained in the storage tank 501:1 is utilized as a washsolution in the subsequent washing of the deposits of UC14 residues fromthe parts disposed in the source regions of the second-stage calutrons.Thus, the condensate contained in the storage tank 501a, after it hasbeen employed as a water wash solution, is placed in the storage tank501 to be treated, as previously noted. Accordingly, this water washsolution, which constitutes a solvent for the UCI-1 residues depositedon the parts disposed in the source regions of the second-stagecalutrons, is recycled.

Also, the plant comprises an electrolytic reducing cell 201, includingan anode compartment and a cathode cornpartment and provided with lamercury cathode. Preferably, the electrolytic cell 201 is substantiallyidentical to the electrolytic cell disclosed in the copendingapplication of Robert Q. Boyer, Serial No. 556,127, filed Sept 28, 1944,which issued as Patent No. 2,733,202 on Jan, 31, 1956. Details of theoperation of such an electrolytic cell are disclosed in said applicationand patent. The electrolytic cell of such application was an improvementof the cell disclosed in application S. N. 532,162, tiled Apr. 2l, 1944and which issued as Patent No. 2,743,228 on Apr. 24, 1956. As disclosedtherein and also as disclosed in divisional application S. N. 615,467,tiled Sept. 10, 1945, now Patent No. 2,775,552, dated Dec. 25, 1956,derived therefrom, electrolytic currents of approximately 0.2 ampere percm.2 were obtained with the aforesaid cell with the usual operatinglimits being 0.1 to 0.3 ampere per cm2. The electrolytic currentsmentioned were obtained with a direct current potential of severalvolts, i. e., about four volts. The anode compartment of theelectrolytic cell 201 contains a suitable quantity of 3 N HCl as ananolyte; and the cathode compartment of the electrolytic cell 201 isconnected to the second-stage evaporator unit 103, whereby theconcentrated wash solution from the evaporator unit 103 is employed as acatholyte. Further, the cathode compartment of the electrolytic cell 201is connected to a cooler 202, which in turn is connected to aprecipitation tank 203. The cooler 202 is supplied with cooling waterfrom a source, not shown; and the precipitation tank 203 is connected toa mixing tank 204 provided with a heating element 205 and connected tosuitable sources of 3 N HC1 and oxalic acid, not shown.

ln the plant arrangement, the concentrated wash solution delivered fromthe second-stage evaporator unit 103 to the cathode compartment of theelectrolytic cell 201 is rendered approximately 3 N in HC1, due toconcentration in the evaporator units 101 and 103, and contains theions: UO2++, Fe+++, Cr+++, Ni++, and Cu++, as previously noted. lnpassing through the cathode compartment of the electrolytic cell 201,this solution is electrolyzed, whereby the UO2++ and the Fe+++ ions arereduced to U++++ and Fe++ ions, and a considerable amount of the Cu++ion is plated out into the mercury cathode, as explained more fullyhereinafter. Accordingly, the solution delivered from the cathodecompartment of the electrolytic cell 201 into the cooler 202 and thenceinto the precipitation tank 203 is about 3 N in HC1 and contains thefollowing ions: U++++, Fe++, Cr+++, Ni++, and Cu++. Subsequently, whenthe warm miture of 3 N HC1 and oxalic acid is delivered from the mixingtank 204 into the precipitation tank 203, the solution delivered fromthe cooler 202 into the precipitation tank 203 is reacted, whereby theuranium is precipitated as U( C2002' 6H2O away from the ions: Fe++,Cr+++, Ni++, and Cu++ to produce a slurry.

Further, the plant comprises filtration apparatus 300, including aiiltering tank 301, a washing tank 302, a drying tank 303, a scrapingtank 304, a cleaning tank 305, and a number of lters of the candle type,five being illustrated at 306, 307, 308, 309, and 310 in the respectivetanks 301, 302, 303, 304, and 305. Preferably each of the candle iiltersis of porous ceramic construction, being formed of Alundum or the like.The ltering tank 301 is connected to the precipitation tank 203, whilethe washing tank 302 is connected to a mixing tank 311 provided with aheating element 312 and connected to suitable sources of l N HC1 andoxalic acid, not shown. The drying tank 303 is connected to a storagetank 313 containing a quantity of a suitable liquid drying agent, such,for example, as substantially anhydrous methyl alcohol, as explainedmore fully hereinafter. The scraping tank 304 is connected to apulverizer 314 disposed therebelow; and the cleaning tank 305 isconnected to a suitable source of sodium hypochlorite solution, notshown. The candle tilters 306 and 307 are connected by way of manuallyadjustable valves 315 and 316, respectively, to a pump 317, which inturn is connected to a storage tank 318, whereby a cake of U(C2O4)2'6H2Oprecipitate may be loaded upon the candle iilter 306 from the slurrydelivered from the precipitation tank 203 into the filtering tank 301,and the wash solution contained in the washing tank 302 may bepercolated through a cake of U(C2O4)2'6H2O precipitate carried by thecandle iilter 307, for a purpose more fully explained hereinafter. Thecandle filter 308 is connected by way of a manually adjustable valve 319to a pump 320, whereby the substantially anhydrous methyl alcohol may bepercolated through a cake of U(C2O4)V26H2O percipitate carried by thecandle lilter 308. This arrangement effects drying of the cake ofprecipitate carried by the candle filter 308 and converts theU(CzO4)z-6H2O to U-(C2O4)2H2O, the methyl alcohol being renderedhydrous, all in a manner more fully explained hereinafter.

The pump 320 is connected to a solvent still 701, which is indirectlyheated by a steam coil connected to a suitable source of steam, notshown. Also, the solvent still 701 is connected to an associatedcondenser 702 supplied with cooling water from a source, not shown;which condenser 702 is connected to the storage tank 313 for a purposemore fully explained hereinafter.

A cake of U(C: .O4)2H2O precipitate carried by the candle lilter 309 maybe unloaded therefrom in the scraping tank 304, whereupon it falls intothe pulverizer 314 in which it is broken up or pulverized into a tinelydivided state. From the candle filter 310 there has been previouslyunloaded a cake of U(C2O4)2H2O precipitate in the scraping tank 304; andin the cleaning tank 305 the candle filter 310 is washed in thecontained solution of sodium hypochlorite in order to remove therefromany residues of the cake of precipitate and again to open the pores inthe wall of the candle iilter 310, whereby the candle iilter 310 isrendered suitable for re-use in the filtering tank 301. Thus it will beunderstood that any given candle filter 306,

V307, 308, 309, or 310 is employed progressively in the tanks 301, 302,303, 304, and 305 in a cyclic manner more fully explained hereinafter.

Also, the plant comprises a calciner 401 of any suitable type, which isassociated with the pulverizer 314 and connected toa source of dry airunder moderate pressure, not shown. The pulverized U(C2O4)2-H2O isdelivered from the pulverizer 314 to the calciner 401, wherein it isconverted to UaOs in a manner more fully explained hereinafter; whichUsOa is delivered to associated electrostatic precitating apparatus 402of the Cottrell type. The precipitating apparatus 402 is connected to anabsorbing tower 403, whereby reaction gases from the calciner 401 areiirst subjected to electrostatic precipitation in the precipitatingapparatus 402 and then delivered to the absorbing tower 403, asexplained more fully hereinafter. The absorbing tower 403 is open to theatmosphere and is connected to a pump 404, which in turn is connected toa storage tank 405 containing a suitable caustic soda solution, thestorage tank 405 being also connected to the lower portion of theabsorbing tower 403, whereby the caustic soda solution may be pumpedfrom the storage tank 405 by the pump 404, sprayed through the absorbingtower 403, and returned back to the storage tank 405 in a cyclic manner.The arrangement of the absorbing tower 403 prevents the escape to theoutside of any uranium contained in the reaction gases deliveredthereto; and periodically the caustic soda solution contained in theassociated storage tank 405 is removed therefrom and subjected tosalvage treatment in order to recover the contained uranium, asexplained more fully hereinafter.

A reactor S01 of the rotary type is associated with the precipitatingapparatus 402; and UaOa is delivered from the lower portion of theprecipitating apparatus 402 to the reactor 801, wherein it is reactedwith CC14 in the vapor phase to produce UCl4. Preferably, the rotaryreactor 801 is substantially identical to the rotary reactor disclosedin the copending application of Horace R. McCombie Edward L. Wagner,Serial No. 523,602led February 23, 1944 which issued Y as Patent No.2,735,746 on February 21, 1956. Also, the reactor 801 is connected to asourcev of dry CO2 under moderate pressure, not shown, and to a storagetank 802 containing liquid CC14, the storage tan'k 802 being connectedto a suitable source of liquid CCli, not shown. Also, the reactor 801 isconnected to associated electrostatic precipitating apparatus 803 of theCottrell type, provided witha condenser 804 which is supplied withcooling water from a source, not shown. The precipitating apparatus 803is also connected Vto the absorbing tower 403, whereby reaction gasesfrom the reactor 801 are first subjected to electrostatic precipitationin the precipitating apparatus 803 and then delivered to the absorbingtower 403, as explained more fully y hereinafter. Vaporous CCL:z is alsodelivered from the reactor 801 into the precipitating apparatus 803along with the reaction gases, and is condensed by the condenser 804 andconducted to a solvent still 805 associated with the precipitatingapparatus 803. The solvent still 805 is connected to a suitable sourceof dry steam, not shown, and 'also to an associated condenser 806supplied with cooling water from a source, not shown. Also the condenser806 preferably includes a communicating settling chamber (not shown)into which flows mixed condensate comprisstantially completely dehydrateit prior to returning it to i the storage tank 802. This may beaccomplished in any convenient manner, such as by passing the wet CCL;through a drying column (not shown) packed with particles of a soliddesiccant material such as anhydrous magnesium perichlorate, fusedcalcium chloride, or the like.

The UCl4 produced in the reactor 801 is delivered therefrom and loadedinto calutron charge bottles, one of which is illustrated at 807, whichare subsequently sealed to retain thecharges of UCI-i in anhydrouscondition. The vbottles 807.illed with the charges of UCL; are againemployed in the ion source units of the second-stage calultrons, in viewof the fact that the uranium in these charges is singly enriched withU235 with respect to natural or normaluranium, as previously noted andas disclosed in the previously mentioned application of Carter andKamen.

Further, the plant comprises an oxidation tank 601 which is connected tothe storage tank 318, whereby the filtrate percolated through the candlefilter 306, as well as the wash solution percolated through the candlelter 307,

to the oxidation tank 601. The electrolytic cell 201 also comprises avclosed hood into which nitrogen from a source, n ot shown,.isdelivered, which serves to sweep *therefrom chlorine liberated thereinincident to operation;

which hood is connected to the oxidation tank 601, whereby the mixtureof nitrogen and chlorine swept from the hood of the electrolytic cell201 is bubbled through the solution contained in the oxidation tank 601.The solution delivered from the ,storage tank 318 to theoxidation tank601 contains Fe++, Cr+++, and Ni++ ions, as well Vas small amounts ofU++++ and Cu++ ions; thewater delivered from the Vs olvent still 7 01 tothe oxidation tank 601 contains some U++++ ion; and the sodiumhypochlorite solution delivered from the cleaning tank 305 to theoxidation tank 601 contains considerable UO2++ ion. Accordin'gly, inthe( oxidation tank 601, the sodium hypochlorite solution in conjunctionwith the chlorine present oxidizes the composite solution containedtherein, whereby a solution containing UOziLi', Fe+++, Cr+++, Ni++, andCu++ ions isproduced; which last-mentioned solution is delivered to anassociated precipitation tank 602. Also, the oxidation tank 601 isconnected to the absorbing tower 403whereby any gases produced thereinincident to oxidation of the solution mentioned are conducted to theabsorbing tower 403 in order that there may be reclaimed therefromanycontained uranium, as previously noted. The Yprecipitation tank 602is connected to a suitable sohrceo'f NH4OH, not show n', whereby theuranium, iron, and chromium may be precipitated away from the nickel andcopperlin the contained solution to produce a slurry containing(NH4)2U2O7, Fe(OH)3, and f(Cr(OH)a precipitate, and Ni(NH3)4++ andcomplexes. The precipitation tank 602 is connected to a pressure lter603, whereby the slurry mentioned may be delivered from theprecipitation tank 602 to the pressure tilter 603 and the precipitateseparated from the slurry. The pressure filter 603 is connected to adissolving tank 604 and to an evaporator 703, whereby the (NH4)2U2O7,Fe(OH)3 and Cr(OH)3 precipitate may be delivered tothe dissolving tank604, and a filtrate containing the Ni(NHs)4J+ and Cu(NH3)4++ complexesmay be delivered-to the evaporator 703. The dissolving tank 604 isconnected to a suitable source of 4 N HC1, not'shown, whereby thecontained precipitate may be dissolved. v

' Further, the plant comprises an electrolytic salvage 'cell 605,including an anode compartment and a cathode vcompartment and providedwith a mercury cathode. Preferably, the electrolytic cell 605 issubstantially identical to ythe electrolytic cell disclosed in thepreviously- 'mentioned application of Robert Q. Boyer, Serial No.556,127, tiled Septembe1f28, 1944 which issued as Patent No. 2,733,202on January 3l, 1956, Details of the operation' of `such cell 605 aresimilar to those described fab'ove in connection with the operation ofcell 201. Also, Vthe electrolytic cell 605 comprises a closed hood intovwhich nitrogen from a source, not shown, is delivered, which serves tosweep therefrom chlorine liberated therein incidentrto operation, asexplained more fully hereinafter. The hood of the electrolytic cell 605is also connected to the oxidation tank 601, whereby the mixture ofynitrogen and chlorine from the electrolytic cell 605 is Ywhereby theHC1 solution contained in the dissolving tank 604 may be delivered tothe electrolytic cell 605 to 'be electrolyzed. Also, the cathodecompartment of the .electrolytic cell 605 is connected to the oxidationtank v502, whereby the electrolyzed solution contained in the cathodecompartment of the electrolytic cell 605 may be delivered to theoxidation tank 502. The HC1 solution delivered from the dissolving tank604 to the cathode compartment of the electrolytic cell 605 is about 3 N`in HC1 and contains UO2++, Fe+++, and Cr+++ ions;

and when it is electrolyzed in the electrolytic cell .605,V

substantially, all of the Fe+++ and Cr+++ ions contained thereiny areplated out into the mercury cathode, and the uraniumtis reduced fromUO2++ ion to U++++ ion., Thus, the electrolyzed solution delivered fromthe Vcathode compartment of the'electrolytic c ell 605 to the oxidation4tank' 502 contains `U++1F+ ion and traces of ``Furthefthe plantcomprises ascrubbercolumn 503,

connected to a suitable source of Water, not shown, and a scrubbercolumn 504 connected to a suitable source of HNO, not shown. Also, thescrubber column 503 is connected to the electrolytic cells 201 and 605,whereby mercury from the cells containing copper, nickel, iron, andchromium, and a small amount of U++++ ion may be delivered thereto. Moreparticularly, the upper portion of the scrubber column 503 comprises acapillary device, not shown, whereby the mercury delivered thereto isdivided into extremely small globules and dropped into` the containedcolumn of water, in order that they may be thoroughly scrubbed incidentto passage therethrough. Also, the scrubber column 503 is connectedadjacent the lower portion thereof to the oxidation tank 502,`wherebywater may be delivered from the-scrubber column 503 into the oxidationtank 502. Preferably, water is continuously supplied to the upperportion of the scrubber column 503 and delivered therefrom adjacent thelower portion thereof, whereby small amounts of U++++ ion are scrubbedfrom the globules of mercury falling through the scrubber column 503 andare accumulated in the column of water. Thus, the water delivered fromthe scrubber column 503 into the oxidation tank 502 contains some U++++ion.

Also, the scrubber column 504 is connected to the lower portion of thescrubber column 503, whereby mercury accumulating in the lower portionof the scrubber column 503 and containing copper, nickel, iron, andchromium may be delivered thereto. More particularly, the upper portionor" the scrubber column 504 comprises a capillary device, not shown,whereby the mercury delivered thereto is divided into extremely smallglobules and dropped into the contained column of HNOa, in order thatthey may be thoroughly scrubbed incident to passage therethrough. Also,the scrubber column S04 is connected adjacent the 'lower portion thereofto the evaporator 703, whereby HNOS may be delivered from the scrubbercolumn 504 into the evaporator 703. Preferably, HNOa is continuouslysupplied to the upper portion of the scrubber column 504 and deliveredtherefrom adjacent the lower portion thereof, whereby copper, nickel,iron, and chromium are scrubbed from the globules of mercury fallingthrough the scrubber column 504 and are accumulated in the column ofHNOa. Thus, the HNOa delivered from the scrubber column 504 to theevaporator 703 contains copper, nickel, iron, and chromium, and themercury accumulating in the lower portion of the scrubber column 504 issubstantially free of the metals mentioned. The lower portion of the'scrubber column 504 is connected to the electrolytic cells 201 and 605,whereby substantially pure mercury may be supplied from the scrubbercolumn 504 to the mercury-cathodes of the cells mentioned, in a cyclicmanner more fully explained hereinafter.

The evaporator 703 is supplied with dry steam from a source, not shown,whereby the HNOS carrying Cu++, Fe+++, Cr+++, and Nit*L ions deliveredthereto from the scrubber column 504, and the chloride-ammoniumhydroxide solution carrying Ni(NHa)4++ and Cu(NH3)4++ complexesdelivered thereto from the pressure idter 603, may be evaporated todryness. Also, the evaporator 703 is connected to a salt storage bin 704adapted to receive the chloride and nitrate salts of iron, copper,nickel, and chromium produced in the evaporator 703 incident toevaporation of the contained solution; which salts contained in the'salt storage bin 704 are subjected to salvage in a manner more fullyexplained hereinafter. Further, the evaporator 703 is connected to acondenser 705 supplied with cooling water from a source, not shown,whereby the vapors driven from the lsolution contained in the evaporator703 incident to evaporation may be condensed. Finally, the condenser 705is connected to a storage tank 706, whereby the condensate accumulatingin the` condenser 705 may be delivered to the storage tank 706; whichcondensate contained in the storage tank '706 is subjected to salvage ina manner more fully explained hereinafter.

'Ihe over-all operation of the plant arrangement will best be understoodfrom the following description of the processes involved in thetreatment therein of a calutron wash solution in conjunction with thevarious reactions employed. Considering now .in greater detairl thecharacter of the wash solution contained in the storage tank 501, it isnoted that 27 liters of a representative wash solution has approximatelythe following composition by weight:

Grams H2O 26,850 HCl l196 Cr 3A Also, this representative wash solutionmay contain a small amount of suspended U(OH)4 and bits of metalliccopper, as well as the ions UO2++, U++++, Fe+++, Fett, Cu++, Cr+++, andNi++, as previously noted. Accordingly, the wash solution is conductedfrom the storage tank 501 into the oxidation tank 502 and therecontacted with H2O2, whereby the solution is oxidized. As a result ofthe oxidation, all of the uranium is put in solution as uranyl ion,UO2++, suspended copper is put in solution as cupric ion, Cu++, the ironis put in solution as ferric ion, Fe+++, and other dissolved materialsare put in their higher stable oxidation states, if they are not alreadyin such states.

The oxidized solution containing UOzJfl, Fe+++, Cu++, Cr+++, and Nit"Lions is conducted into the first-stage evaporator unit 101, whereby itis concentrated by evaporation and conducted into the storage tank 102.Preferably, the solution is supplied continuously through the manuallyadjustabile valve into the header 104, and conducted continuously fromthe rheader 104 through the manually adjustable valve 106 into `thestorage tank 102, the rates of ow being predetermined by adjustment ofthe valves 105 and 106, so that the solution experiences a reduction involume of the order of 66% due to treatment in the first-stageevaporator unit 101. In other words, during a predetermined timeinterval 30 liters of solution is con-ducted through the valve 105 intothe header 104, and 10 liters of concentrated solution is conducted fromthe7 header 104 through the valve 106 into the storage tank 102, 20liters of this solution having been driven oit as vapor by action of theevaporator 107 of the evaporator unit 101 and condensed in the condenser109. The vapor driven from the solution comprises primjarily watervapor, although it contains a small amount of HC1; andthe condensateaccumulating in the condenser 109 is returned to the storage tank 501a.

The concentrated solution contained in the storage tank 102 is conductedinto the second-stage evaporator unit 103', whereby it is concentratedby evaporation and conducted into the cathode compartment of theeiectrolytic cell 201. Preferably, the solution is supplied continuouslythrough the manually adjustable valve 111 into the header 110, andconducted continuously from the header 110 through the manuallyadjustable valve 112 into the cathode compartment of the electrolyticcell 201, the rates of flow being predetermined by adjustment of thevalves 111 and 112, so that the solution experiences a reduction involume of the order of 90% due to treatment in the second-stageevaporator unit 103. In other words, duringA a predetermined timeinterval, l0 liters of solution is conducted through the valve 111 intoVthe header 110, and one liter of concentrated lsolution is conductedfrom the header 110 through the valve 112 into the cathoode compartmentof the electrolytic cell 201, 9 liters of this solution having beendrivencff as vapor by action of the evaporator 113 of theA evaporatorunit 103 and con-- densed in the condenser 115. T he'vaporidriven fromthe solution comprises primarily water vapor, although itv contains someHC1; land the condensate accumulating in the condenser 115 is returnedto the storage tank 501a.

Each of the evaporator units 101 and 103 iskof the liashboiler type,whereby there is considerable recirculation including the associatedevaporator, the de-entrainment head, and the header in series circuitrelation; which arrangement minimizes entrainment of uranium in thevapor condensing in the associated condensers 109 and 115. However,since the condensates accumulating in `the condensers 109 and 115 anddraining into the storage tank 50111 does contain traces of uranium, thesolution accumulated -in the storage tank 501a is utilized as a washsolution in the subsequent washing'ol:` deposits of vUCla residues fromthe parts disposed in the source regions of the second-stage calutrons,as previously noted.

V=In view of the foregoing description of the mode of operation of theevaporator units 101 and 103, it will be understood that during-apredetermined time interval liters of lsolution from the oxidation tank502 is delivered to the first-stage evaporator unit 101 and one liter ofconcentrated solution is delivered from the second-stage evaporator'unit 103 to the cathode compartment of the electrolytic cell 201,wherebyV the HCl, uranium, iron, chromium, nickel, and copper in thesolution conducted into the cathode compartment of the electrolytic cell201 are considerably concentrated with respect to the solution containedin the `oxidation tank 502.

For example, 0.9 liter of a representative solution conducted from thesecond-stage evaporator unit 103 into the cathode compartment of theelectrolytic cell 201 has approximately the following composition -byweight:

Grams Fe V3 Cr S:

Accordingly, the solution conducted into the cathode compartment of theelectrolytic cell 201 is approximately 3 N in HCl and contains UO2++,Fe+++, Cr+++, Ni++, and Cu++ ions. Y

The anode compartment of the electrolytic cell 201 contains a suitablequantity of 3 N HCl as an anolyte, while the concentrated solutionconductedl from the evaporator unit 103 into the cathode compartment ofthe electrolytic cell 201 constitutes a cathdlyte; whereby the solutionmentioned is electrolyzed, theruranyl and ferric ions, UO2++ and Fe+++,being reduced to uranous and ferrous ions, U++++ and 'Fe++. Also, somechlorine is liberated in the electrolytic cell 201, which accumuv latesin the hood thereof and is swept therefrom by nitrogen supplied thereto,whereby the mixture of nitrogen and chlorine is conducted from the hoodof the electrolytic cell 201 into the oxidation tank 601. Preferably,the concentrated solution from the evaporator unit 103 is continuouslyconducted into the cathode compartment of the electrolytic cell 201 andthis solution, after being electrolyzed, is continuously conductedtherefrom into the cooler 202, the flow being Iat a proper rate in orderto insureV substantially complete reduc-tion of theV uranyl and ferrieions to uranous and ferrous ions as explained above, whereby thesolution conducted from the cathode compartment `of the electrolyticcell 201 into the cooler 202 is approximately 3 N HC1 and contains thefollowing ions: U++++, Fe++, Cr+++, Ni++, and Cu++.

Also, incident to operation of the electrolytic cell 201, aconsiderableamount of the copper and some of the nickel in the solution containedvin the cathode eompart- Y 503. Preferably, freshy mercury from thescrubber column 504 is continuously supplied to the electrolytic cell201 and the mercury therein is continuously delivered to the scrubbercolumn 503, whereby the metal impurities, principally copper and nickel,accumulating in the mercury cathode of the electrolytic cell 201 arecontinuously transported therefrom along with the mercury into thescrubber column 503. In passing through the cathode compartment Vof theelectrolytic cell 201, the solution mentioned is heated considerablyabove room temperature, temperatures of the order of C. being frequentlyencountered; and it'is preferable to operate the cooler y202 under suchconditions that the electrolyzed solution delivered thereto is cooledback to room temperature, approximately 20 C., before it is deliveredvto the precipitation tank 203. The cooling of the electrolyzed solutiondelivered to the cooler 202 from the cathode compartment of theelectrolytic cell 201, before the introduction of this solution into theprecipitation tank 203, is very advantageous Y in that substantialre-oxidation of U+++.+ ion back to UO2++ ion, due to contact with air,is prevented. v y

In the mixing tank 204, there is prepared a saturated solution ofoxa'lic acid in about 3 N HC1, which solution ,is heated to -atemperature of approximately 60 SC. by the heating element 20S in orderto prevent the oxalic acid from crystalizing out. This warm solution ofoxalic acid in approximately 3 NV HCl is conducted in a stoichiometricexcess into the precipitation tank 203, whereby the uranium contained inthe solution supplied to the precipitation tank 203 from the cooler 202is substantially completely precipitated as uranous oxalate away fromthe copper, iron, chromium, and nickel impurities in the solution.Accordingly, a slurry is produced containing U(C2O4)26H2O and \Fe++,Cr+++, yNi++, Cu++, and perhaps a trace of UH'ar ions. The precipitation-of the uranium as uranous oxalate away from the metal impurities in thesolution is most advantageously eifected when the acidity of the slurryproduced is about l 'N to 3 N in hydrogen ion. Y

The slurry produced in the precipitation tank 203 is conducted to thefiltering tank 301 and the valve315 is opened an appropriate amountwhile the pump 317 is operating, whereby a cake of U(CzO4)z-6H2Oprecipitate is loaded upon the exterior surface of the candle filter 306and a filtrate containing Fe++, Cr+++, Ni'tt, Cu++, and a trace of U++++ions is delivered into the storage Itank 318. After a suitable cake ofU(C2O4)26H2O precipitate has been loaded upon the candle filter 306, thevalve 315 Vis closed andthe candle filter 306 is removed Vfromtheliltering tank 301 and placed in the washing tank 302. t

Now assuming that a suitable cake of U(C2O4)26H2O precipitate scarriedby the candle filter 307 arranged in the washing tank 302, thecake of precipitate having been previously loaded upon the candle filter307 in the filtering tank'301 in the manner noted, the valve 316 isopened an appropriate amount while the pump 317 is operating, wherebythe cake of U(C2O4)26H2O precipitate carried by the candle filter 307 iswashed. More particularly, in the mixing tank 311 there is prepared adilute solution of oxalic acid in about 1 N HCl, the solution beingapproximately 0.2 molar in oxalic acid, which solution is heated to atemperature of vapproximately 60 C. by the heating element 312. Thiswarm solution of oxalic acid in approximately l N HCl is conducted intothe washing tank 302 and pereolated through the cake of U(C2O4)26H2Oprecipitate as noted above, the Washrsolution being then delivered intothe storage tank 318; Thus, the filtrate from the filtering tank 301 andthe Wash solution from the'washi'ng tank 302'ar'e delivered by the u 31ions, whereby the wash solution delivered from the wash# ing tank 302 tothe storage tank 318 may contain a trace of U+++Jr ion. After the cakeof U(C2O4)26H2O precipitate carried by the candle filter 307 has beensuitably washed, the valve 316 is closed and the candle filter 307 isremoved from the washing tank 302 and placed in the drying tank 303.

Now assuming that a suitable cake of U(C2O4)z-6H2O precipitate iscarried by the candle filter 308 arranged in the drying tank 303, thecake Vof precipitate having been previously washed in the washing tank302 in the manner noted, the valve 319 is opened an appropriate amountwhile the pump 320 is operating, whereby the cake of U(C2O4)26H2Oprecipitate carried by the candle filter 308 is dried. Moreparticularly, a suitable drying age-nt, preferably substantiallyanhydrous methyl alcohol, is delivered from the storage tank 313 intothe drying tank 303, whereby the substantially anhydrous methyl alcoholis percol-ated through the cake of U(C2O4)2'6H2O precipitate as notedabove, the wash solution being `then delivered by the pump 320 into thesolvent still 701. While the liquid drying agent employed may beselected from a relatively large class including a lower monohydricalcohol (methyl, ethyl, propyl, and isopropyl alcohols), an ether(methylethyl, dimethyl, and diethyl ethers), and

, a ketone (acetone `and methyl-ethyl ketones), it is pref* erable thatthe `drying agent comprise the lower monohydric alcohol, methyl or ethylalcohols, and specifically methyl alcohol. More particularly, any of theliquid drying agents mentioned is effective to remove from the cake VofU(C2O4)2-6H2O precipitate carried by the candle filter 308 occluded ortrapped water, but only certain of these liquid drying agents (methyland ethyl alcohols) have been found effective to remove from the cake ofU(C2O4)26H2O precipitate carried by the candle filter 308 some of thewater of hydration. Specifically, methyl alcohol is particularlyeffective in this regard, causing the U(C2O4)26H2O precipitate to beconverted to U(C2O4)2'H2O, whereby the methyl alcohol percolated throughthe cake of precipitate carried by the candle filter 308 and deliveredto the solvent still 701l is rendered hydrous. Also, the methyl alcoholpercolated through the cake of precipitate carried by the candle filter308 and delivered to the solvent still 701 carries a small amount ofU++++ ion. When the cake of precipitate carried by the candle filter 308is converted from U(C24)2'6H2O to U(C2O4) 2H2O, the color thereof ischanged from green to violet, whereby satisfactory dehydration of thehydrous cake of precipitate carried by the candle tilter 308 may bereadily determined from inspection. After the cake o-f U( C2O4)2-6H2Ocarried by the candle filter 30S has been suitably dried to produce acake of U(C2O4)2H2O precipitate as noted above, the valve 319 is closedand the candle filter 308 is removed from the drying tank 303 and placedin the scraping tank 304.

Now assuming that a suitable cake of U(C2O4)2-H2O is carried by thecandle filter 309 arranged in the scraping tank 304, the cake ofprecipitate having been previously dried in the drying tank 303 in themanner noted, the candle lter 309 is rotated about its axis, wherebyscraping mechanism, diagrammatically illustrated, incorpo rated in thescraping tank 304 unloads the cake of U(C2O4)2H2O from the candle filter309 and scrapes the exterior surface thereof, whereby the U(C2O4)2H2Oprecipitate falls into the pulverizer 314. The

precipitate is bnoken up and placed in finely divided form bypulverizing mechanism, diagrammatically illustrated, incorporated in thepulverizer 314. The U(C2O4)z-H2O accumulating in the lower portion ofthe pulverizer 314 is delivered to the calciner 401; and after thecandle filter 309 has been appropriately scraped in the scraping tank304 in order to remove therefrom substantially all of the cake ofU(C2G4)2'H2O precipitate carried thereby, the

candle filter 309 is removed from the scraping tank 304 land' placed inthe cleaning tank 305.

Now assuming that the candle ilter 310 arranged in the 4cleaning tank305 has previously had a cake of U(C2O4)2-H2O precipitate unloadedtherefrom in the scraping tank 304 in the manner noted, a small amountof U(C2O4)2H2O is carried thereby and the pores in the wall thereof areat least partially blocked by the compound mentioned. The surfaces ofthe candle filter 310 are thoroughly washed with a hypochlorite solutioncontained in the cleaning tank 305. Preferably, the solu tion mentionedcomprises sodium hypochlorite, as this material is very effective inwashing from the surfaces of the candle filter 310 any U(C2O4)2-H2Odeposited thereon and in opening the pores of thewall of the candlefilter 310. Also, the uranous oxalate is decomposed and the containeduranium is placed in solution as UO2++ ion due to the presence of OCl*anion in the solution, the U++++ ion being oxidized to UO2++ ion. Thesodium hypochlorite wash solution is delivered from the cleaning tank30S int-o the oxidation tank 601, and an excess quantity of sodiumhypochlorite solution isV employed in washing the candle filter 310, sothat considerable unreacted sodium hypochlorite solution is deliveredinto the oxidation tank `601 lfor use therein, as more fully explainedhereinafter. After the surfaces of the candle filter 310 have beenthoroughly washed in the cleaning ltank 30S, the candle filter 310 isremoved from the cleaning tank 305 and placed in the `filtering' tank301. Thus, the candle filters 306, 307, 308, 309, and 310 are placedsuccessively in the tanks 301, 302, 303, 304, and 305 in a cyclicmanner, and it will be understood that in fact it is not necessary toemploy five such candle tilters, as it will be apparent that even onecandle filter will sufiice in the cyclic process or that a number ofcandle til-ters larger than five may be employed as a matter ofconvenience.

The pulverized U(C2O4)2H2O is delivered from the lower portion of thepulverizer 314 as a charge to one end of the calciner 401, along with astream of dry air, wherein it is heated to a temperature ofapproximately 500 C., whereby the U(\C2O4)2H2O is converted to UaOe,reaction gases and vapors including CO, CO2, and H2O being producedincident to the calcination. The other end of the calciner 401 isconnected to the precipitating apparatus 402 and the product, UaOa,along with the reaction gases, is delivered to the precipitatingapparatus 402, whereby UaOs accumulates in the lower portion of theprecipitating apparatus 402 and the reaction gases, as well as air,proceed up through the precipitating apparatus 402 into the absorbingtower 403. The precipitating apparatus 402 -is effective to causeelectrostatic precipitation of a majority of the finely divided UaOcontained in the stream of reaction gases and vapors delivered to theabsorbing tower 403, whereby only a small amount of uranium istransported from the precipitating apparatus 402 into the absorbingtower 403.

The UsOs accumulating in the lower portion of the precipitatingapparatus 402 is continuously delivered into one end of the rotaryreactor 801, and dry CO2 and liquid CC14 are introduced into `the otherend of the rotary reactor 801. The liquid CCL; is converted into Vaporand reacted with the UaO lin the presence of the CO2 atmosphere at atemperature within the range 425 to 475 C. in order to produce UC14 andreaction gases including COClz, CO, CO2, and C12, along with a minoramount of UCl5 in lthe form of a finely divided smoke. The product,UC14, produced in the rotary reactor 801 is continuously deliveredtherefrom and loaded into the calutron charge bottles 307. Preferably,the bottles 807 are sealed in order .to preserve the anhydrous conditionof the charge of UCl4; which charge bottles 807 are employed in the ionsour-ce units of the second-stage calutrons, as previously noted.

The reaction gases, the UCl5, and considerable amounts of CC14 vapor aredelivered from the rotary reactor 801 into the precipitating apparatus803, which is effective to precipitate electrostatically substantiallyall of the UCls contained in the gases and vapor mentioned. Also, thecondenser 804 associated with the precipitating apparatus-803 iseffective to condense substantially all of the CCl4 vapor, which CC14condensate accumulates in the lower portion of the precipitatingapparatus 803, carrying with it substantially all of the UClsprecipitated, in view of the fact that UCls is fairly soluble in CC14.The gaseous reaction products, COClz, CO, CO2, and Clz, continue throughthe precipitating apparatus 803 and are delivered into the absorbingtower 403, while the liquid CCL; and the UCls accumulating in the lowerportion of the precipitating apparatus 803 are delivered into thesolvent still 805.

Accordingly, from the precipitating apparatus 402 and 803, COClz, C12,CO, CO2, air, and H2O gases and vapor are delivered into the absorbingtower 403 and contacted with the finely divided spray of NaOH therein,the NaOH being continuously recirculated through the lower portion ofthe absorbing tower 403, the storage tank 405, the pump 404, and theupper portion of the absorbing tower 403. Thus, the gases and vapormentioned are thoroughly washed with the NaOH spray, thereby positivelyIto scrub Vtherefrom any contained uranium in order to prevent lossthereof to the outside. Also, the sodium hydroxide readily absorbs theCO2 gas and readily reacts the COClz and Clz gases, whereby the twolast-mentioned noxious gases are prevented from being exhausted to ytheatmosphere from the upper portion of the absorbing tower 402. It will,of course, be understood that COClz and Clz gases are reacted with NaOHto produce a carbonate and chloride and hypochlorite solution.Occasionally, the liquid contained in the storage tank 405 may besubjected to salvage in order to reclaim any contained uranium; and thescrubbed gases areV discharged from the upper portion of the absorbingtower 403 to the atmosphere as previously noted.

The hydrous methyl alcohol, containing small amounts of U++++ ion,percolated through the cake of precipitate carried by the candle filter308 is delivered by the pump 320-into the solvent still 701, aspreviously noted, and is therein subjected to fractionation, wherebysubstantially anhydrous methyl alcohol vapor is liberated in the solventstill 701 and condensed in the condenser 702, and water containing U++++ion accumulates in' the lower portion of the solvent still 701, Thesubstantially anhydrous methyl alcohol condensate accumulating inthe'condenser 702 is delivered back to the storage tank 313, whereby itmay be again conducted into the drying tank 303 in a cyclic manner;while the water containing U++++ ion accumulating in the lower portionof the solvent still 701 is delivered to the oxidation tank 601, aspreviously noted.

The liquid CCl4, containing UCls, is delivered from the lower portion ofthe precipitating apparatus 803 to the solvent still 805, as previouslynoted, and is therein subjected to distillation by direct contact withdry steam, whereby CCI.; vapor is liberated in the solvent still 805and, together with water vapor, is condensed in the condenser 806, andwater containing UO2++ and U++++ ions accumulates in the lower portionof the'solvent still 805. The mixed condensate comprising CClr andwateris subjected to layer formation for the separation of CCM and water,Vthe latter being removed and discarded or subjected to further salvageoperations, while if desired the former is subjected to dehydration toVsubstantially completely remove any residual water which it may contain,after which it is delivered back to the storage tank 802, whereby it maybe again conducted into the rotary reactor 801 in a cyclic manner;whilethe water contain-` ing the UO2++ and U++++ ions accumulating inthe-lower portion Vof the solvent still 805 comprises a solution whichis conducted directly back intothe cathode compartment of theelectrolytic cell 201, as previously noted.

The solution delivered from the storage tank 318 to the oxidation tank601 comprises an oxalic acid solution containing VFett, Cr+++, and Ni++ions, as well as small amounts of U++++ and Cu++ ions; the waterdelivered from the solvent still 701 to the oxidation tank 601 containssome U+++1L ion; and the sodium hypochlorite solution delivered from thecleaning tank 305 to the oxidation tank 601 contains considerable UO++ion. Accordingly, in the oxidation tank 601 the sodium hypochloritesolution in conjunction with the chlorine present oxidizes the compositesolution contained therein, whereby a solution containing UO2++, Fe+++,Cr+++, Ni++, and Cu++ ions is produced. As previously noted, themixtures of nitrogen andchlorine are delivered into the oxidation tank601 from the hoods of the electrolyti-c cells 201 and 605 and arebubbled through the composite solution; while the upper portion of theoxidation tank 601 is connected to the absorbing tower 403, whereby anyuranium contained in the gases delivered from the oxidation tank 601 tothe absorbing tower 403 is reclaimed in the absorbing tower 403 in themanner previously explained. Also, it will be understood that incidentto oxidation of the ions mentioned to their higher stable oxidationstates, the oxalic acid solution is also decomposed by chlorine andhypochlorite ion oxidation, whereby CO2 is produced which is deliveredalong with Vexcess C12 and nitrogen from the oxidation tank 601 to theabsorbing tower 403, as previously noted. Preferably, the sodiumhypochlorite solution employed in cleaning the candle lters in theIcleaning tank 305, and subsequently in oxidizing the oxalic acidsolution in the oxidation tank 601, is substantially free of basichydroxide, and a solution is employed which contains approximately 2.6%sodium hypochlorite by weight and which has a pH of approximately. 9.7prior to liberation of the available chlorine. A commercially availablesodium hypochlorite solution, sold under ythe trademark Clorox, has beenfound to be quite satisfactory when diluted as indicated above. The

utilization 1of a sodium hypochlorite solution of the general characterspecied has been found very advantageous, in that the normal tendency ofthe UO2++ ion to precipitate as NazUzOr after the solution has stood awhile is prevented.

The solution containing UO2++, Fe+++, Cr+++, Ni++, and Cu++ ionsdelivered from the oxidation tank 601 to the precipitation tank 602 issubjected therein to ammonia treatment, either with excess NH3 orcarbonate-free NH4OH, whereby (NH4)2U2O7, Fe(OH), and Cr(OH)3 areprecipitated away from most of the copper and nickel in solution in theform of ammonia complex ions Cu(NH3)4++ and Ni(NH3)4++; and this slurryis delivered to the pressure lter 603. In the pressure filter 603, theprecipitate of (NH4)2U2O7, Fe(OH)a, and Cr(OH)s is separated from theslurry and a filtrate is produced containing the Ni(NH3)4++ andCu(NH3)4++ complexes, the precipitate being delivered to the dissolvingtank 604 and the ltrate being delivered to the' evaporator 703, aspreviously noted. In the dissolving tank 604,'the (NH4)2U2O7, Fe(Ol-I)a,and Cr(OH)3 precipitate is dissolved in an excess of 4 N HC1, wherebyafter dissolution. there is produced a 3 N' HC1 solution containingUO2++, FeLl-, and Cr+++ ions, which solution is delivered as a catholyteto the cathode compartment of the electrolytic cell 605, the anode com-Cr+++ ions contained therein are platedout into the mercuryV cathode andthe. to U++++.im, tank 604 il .gnl

after being electrolyzed is continuously conducted therefrom into theoxidation tank 502, the ow being at a proper rate in Iorder to insuresubstantially complete plating out of the iron and chromium into themercury cathode and substantially complete reduction of the uranyl ionto the uranous ion, as explained above. Thus, this solution conductedfrom the cathode compartment of the electrolytic cell 60S into theoxidation tank 502 comprises a HC1 solution containing U++++ ion. Also,some chloline is liberated in the electrolytic cell 605, whichaccumulates in the hood thereof and is swept therefrom by nitrogensupplied thereto, whereby the mixture of nitrogen and chlorine isconducted from the hood of the electrolytic cell 605 into the oxidationtank 601, as previously noted.

Preferably, fresh mercury from the scrubber column 504 is continuouslysupplied to the electrolytic cell 605 and the mercury therein iscontinuously delivered to the scrubber column 503, whereby the metalimpurities, principally iron and chromium, accumulating in the mercurycathode of the electrolytic cell 605 are continuously transportedtherefrom along with the mercury into the scrubber column 503, VAlso,the mercury conducted from the cathode of the electrolytic cell 605 tothe scrubber column 503 carries a small amount of U++++ ion therewithalong with the metal impurities mentioned, the U++++ ion beingmechanically trapped in the mercury incident to operation thereof.

The mercury from the electrolytic cell 201 and the mercury from theelectrolytic cell 605 are combined, whereby the composite mercuryintroduced into the scrubber column 503 contains copper, nickel, iron,and chromium impurities, as well as a small amount of U++++ ionmechanically trapped therein. Preferably, the mercury mentioned iscontinuously conducted to the upper portion of the scrubber column 503and is divided into small globules by the capillary device and droppedthrough the water column, whereby it is thoroughly scrubbed and theU++++ ion is placed in the water solution. Preferably, water iscontinuously supplied to the upper portion of the scrubber column 503and is continuously delivered therefrom adjacent the lower prtionthereof and conducted into the oxidation tank 502, whereby the solutionintroduced into the oxidation tank 502 contains U++++ ion.

Preferably, the mercury containing copper, nickel, iron, and chromiumimpurities accumulating in the lower portion of the scrubber column 503is continuously conducted into the upper portion of the scrubber column504 and is divided into small globules by the capillary device anddropped into the HNOa column, whereby it is thoroughly scrubbed and thecopper, nickel, iron, and chromium impurities are placed in solution asCu++, Ni++, Fe+++, and Cr+++ ions. Preferably, the HNOs is continuouslysupplied to the upper portion of the scrubber column 504 and iscontinuously delivered therefrom adjacent the lower portion thereof andconducted into the evaporator 703. Preferably, the clean mercuryaccumulating in the lower portion of the scrubber column 504 iscontinuously supplied to the electrolytic cells 201 and 605, aspreviously noted.

The nitrate solution from the scrubber column 504, carrying Cu++, Cr+++,Fe+++, and Ni++ ions, is combined with the chloride-ammonium hydroxidesolution from the pressure filter 603 carrying Ni(NH3)4++ andCu(NH3)f-i++ complexes, and this composite solution is delivered to theevaporator 703, wherein it is evaporated to dryness. The chloride andnitrate salts of iron, copper, nickel, and chromium produced in theevaporator 703 are delivered to the salt storage bin 704 and aresubsequently subjected to salvage in order to recover therefrom anytraces of contained uranium. The vapor liberated in the evaporator 703is condensed in the condenser 705 and this condensate is delivered tothe storage tank 706, and is subsequently subjected to salvage in orderto recover therefrom any traces of contained uranium.

The solution containing U++++ ion from the scrubber column 503 and thesolution containing UfffL ion from the cathode compartment of theelectrolytic cell 605 are combined to produce a composite solutiondelivered to the oxidation tank 502, wherein'the composite solution ismixed with the solution delivered to the oxidation tank 502 from thestorage tank 501, which iinal solution is then contacted with H2O2 inorder that all of the uranous ion is oxidized to uranyl yion, aspreviously explained.

In view of the foregoing description lof the processes involved in thetreatment of a calutron wash solution in the plant arrangement, it willbe understood that various combinations of steps have been employed toprovide cyclic operation, and that substantially all of the iiltrates,precipitates, and other reaction products produced incident to carryingout the various steps of the processes are subjected to appropriatesalvage treatments in order to prevent loss of the contained uranium tothe outside, whereby the plant arrangement is highly eicient in theconservation of uranium enriched with U235 with respect to natural ornormal uranium and effects eflicient overall operation of the calutronmethod of producing uranium enriched with the isotope U235.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modications as fall within the truespirit and scope of the invention.

What is claimed is:

1. The process of reclaiming uranium values from the parts of a calutronupon which it is deposited comprising Washing the parts mentioned with asolvent for .the uranium, whereby uranyl ions and the ions of metalimpurities of a class that forms soluble oxaltes in acid solution areintroduced in the wash solution, subjecting the wash solution to areducing treatment to convert the uranyl into uranous ions in thesolution, then treating the solution with a stoichiometric excess ofoxalfic and hydrochloric acids to precipitate the uranium as uranousoxalate away from metal impurities in the solution forming a slurrywhich is about l to 3 N in hydrochloric acid, separating the wet uranousoxalate precipitate from the solution, contacting the wet uranousloxalate precipitate with a suitable liquid drying agent, whereby thewet uranous oxalate precipitate is dried, and then calcining the drieduranous oxalate precipitate to produce `a uranium oxide.

2. The process of reclaiming uranium values from the parts of a-calutron upon which it is deposited comprising washing the partsmentioned with a solvent for the uranium, whereby uranyl ions and theions of metal impurities of a class that forms soluble oxalates in acidsolution are introduced in the wash solution, subjecting the washsolution to a reducing treatment to convert the uranyl into uranous ionsin the solution, then treating the solution with a stoichiometric excessof oxalic and hydrochloric acids Ito precipitate the uranium as hydrousuranous oxalate away from the metal impurities in the solution forming aslurry which is about l to 3 N in hydrochloric acid, separating thehydrous uranous oxalate precipitate from the solution, contacting thehydrous uranous oxalate precipitate with a suitable liquid drying agent:to remove therefrom some wat-er of hydration, and then calcining thepartially dehydrated uranous `oxalate precipitate to produce a uraniumoxide.

3. The process of reclaiming uranium values from the parts of a calutronupon which it is deposited comprising washing `the parts mentioned witha solvent for the uranium, whereby uranyl irons and the ions of metalirnpurities lof a class that forms soluble oxalates in acid solution areintroduced in the wash solution, subjecting the Wash solution to areducing treatment to convert the (19 uranyl into uranous ions in thesolution, then treating the solution with a stoichiometric excess ofOxa-lic and hydrochloric acids to precipitate the uranium as uranousoxalate hexahydrate away from the metal impurities in the solutionforming a slurry which is about l to 3 N in hydrochloric acid,separating the uranous oxalate hexahydrate precipitate from thesolution, contacting the uranous oxalate hexahydrate precipitate with asuitable liquid drying agent to produce uranous oxalate monohydrate, andthen calcining the uranous oxalate monohydrate to produce a uraniumoxide.

4. The process of reclaiming uranium values from the parts of a calutronupon which it is deposited comprising washing the parts mentioned withasolvent for the uranium, whereby uranyl ions and the ions of metalimpurities of a class that forms soluble oxalates in `acid solution areintroduced in the wash solution, subjecting the wash solution to areducing treatment to convert uranyl into uranous ions in the solution,then treating the solution with 'a stoichiometric excess of oxalic andhydrochloric acids to precipitate the uranium as uranous oxalatehexahydrate away from the metal impurities in the solution forming aslurry which is about l to 3 N in hydrochloric acid, separating theuranous oxalate hexahydrate precipitate from the solution, contactingthe uranous oxalate hexahydrate precipitate with a substantiallyanhydrous lower monohydric alcohol to produce uranous oxalatemonohydrate, and then calcining the uranous oxalate monohydrate toproduce a uranium oxide.

5. The process of reclaiming uranium values from the parts of calutronupon which `it is deposited comprising washing the parts mentioned witha solvent for the uranium, whereby uranyl ions and the -ions of metalimpurities of a class that forms soluble oxalates in acid solution areintroduced in the Ywash solution, subjecting the wash solution to areducing treatment to convert the uranyl into uranous ions in thesolution, then treating the solution with a stoichiometric excess ofoxalic and hydrochloric acids to precipitate the uranium as uranousoxalate hexahydrate away from the metal impurities in the solutionforming a slurry which is about l to 3 N in hydrochloric acid,separating the uranous oxalate hexahydrate precipitate from thesolution, contacting the uranous oxalate hexahydrate precipitate with asubstantially anhydrous lower monohydric alcohol to produce uranousoxalate monohydrate, whereby the alcohol is' rendered hydrous, calciningthe uranous oxalate monohydrate to produce `a uranium oxide,fractionating the hydrous alcohol to render it substantially anhydrous,recovering the water separated from the `alcohol incident tofractionation, reclaiming any fraction of uranium contained in therecovered water, and then contacting another uranous oxalate hexahydrateprecipitate with the fractionated substantially anhydrous alcohol.

6. The process comprising loading hydrous uranous oxalate precipitatecontained in a slurry containing impurities of a class which Iformssoluble oxalates in acid solution upon a candle filter to form a cake,Vpercolating through the cake of hydrous uranous oxalate precipitatecarried by the candle filter a wash solution of oxalic and hydrochloric`acids to remove residual impurities of said class, then percolatingthrough the cake of hydrous uranous oxalate precipitate carried by thecandle filter a suitable liquid drying agent to remove therefrom somewater of hydration, then unloading the partially dehydrated cake ofuranous oxalate precipitate from the candle filter, percolating throughthe candle filter a suitable liquid solvent for uranous oxalate in orderto salvage therefrom any residues of uranous oxalateprecipitate carriedthereby, andV again loading hydrous uranous oxalate precipitatecontained in a slurry upon the candle filter.

7. The process comprising loading uranous oxalate hexahydrateprecipitate contained in a slurrycontaining impurities of a class whichforms soluble oxalates in acid solution upon Va candlev lter to form acake, pereolatng 20 through the cake of uranous oxalatehexahydratelprecipitate carried by the candle filter a wash solution ofoxalic and hydrochloric acids to remove residual impurities of saidclass, thenpercolating through the cake of uranous oxalate hexahydrateprecipitate carried by the candle filter a substantially anhydrous lowermonohydric alcohol'to produce a cake of uranous oxalate monohydratefthenunloading the cake of uranous oxalate monohydrate from the candlefilter, percolating through the candle lter a solution containingOClanion in order to salvage therefrom any residues of uranous oxalatemonohydrate carried thereby, and again loading uranous oxalatehexahydrate precipitate contained in 'a slurry upon the candle filter.

8. The process of reclaiming uranous oxalate from the surfaces ofapparatus upon which it is deposited comprising washing the surfacesmentioned with a solution containing OCl* anion in `a concentrationequivalent to about 2.6% of sodium hypochlorite and havinga pH of about9.7, whereby there is producedl a stable solution of uranyl ion.

9. The process of decomposing uranous oxalate and placing the uranium insolution comprising contacting the uranous oxalate with a solutioncontaining OCI anion in a concentration equivalent to about 2.6% ofsodium hypochlorite and having a pH of about 9.7, whereby there isproduced a stable solution of uranyl ion.

l0. The process of decomposing uranous oxalate and placing the uraniumin solution comprising contacting the uranous oxalate with a solution ofsodium hypochlorite of about 2.6% concentration and having a pH of about9.7, whereby there is produced a stable solution of uranyl lon.

11. The process of reclaiming uranium values from an original solutionalso containing metal impurities of a class .that forms soluble oxalatesin acid solution comprising treating the original solution to produce adilute hydrochloric acid solution containing ions of uranium and metalimpurities in their higher oxidation states, concentrating the dilutesolution by evaporation, subjecting the concentrated solution toelectrolytic treat-ment, thereby to reduce the contained ions of uraniumand metal impurities to their lower oxidation states, treating theelectrolyzed solution with a stoichiometric excess of oxalic andhydrochloric acids to precipitate the uranium as uranous oxalate awayfrom the metal impurities in the solution forming a slurry which isabout l toV 3 N in hydrochloric acid, filtering the solution to separatethe uranous oxalate precipitate therefrom, whereby the filtrate containsthe metal impurities and a fraction of the uranium, treating thefiltrate with hypochrite oxidizing agent to destroy the contained oxalicacid and to oxidize the contained i-ons of uranium and metal impuritiesto their higher oxidation states, then treating the solution withammonium hydroxide to precipitate :the fraction of uranium as ammoniumdiuranate and the metal impui-ities as hydroxides in the solution,filtering the solution to separate the precipitate, dissolving theprecipitate in hydrochloric acid, whereby there are placed in solu tionions of uranium and the metal impurities in their higher oxidationstates, subject-ing the solution .to electrolytic treatment in ordersubstantially to plate out of solution the contained metal impurities,thereby to produce an electrolyzed solution containing the fraction ofuranium and a fraction of the meta-l impurities, and then producing acomposite solution from which uranium is to be reclaimed of the treatedsolution and another original solution of the character mentioned.

l2. The process of salvaging a fraction of uranium from a solution alsocontaining metal impurities comprising subjecting the solution t0 t cellprovided with a m t t tially to plate outY the contamd fraction ofuranium and only a fraction of the metal impurities and a mercurycathode containing a trace of the uranium and substantially all of themetal impurities, and lthen separately recovering the uranium containedin both the electrolyzed solution and the mercury cathode.

13. The process of salvaging a fraction of uranium from a solution alsocontaining metal impurities comprising subjecting the solution totreatment in an electrolytic cell provided with a mercury cathode in-order substantially to plate out of the solution into the mercurycathode the contained metal impurities, thereby to produce anelectrolyzed solution containing substantially all of the fraction ofuranium and only a fraction of the metal impurities and a mercurycathode containing a trace of the uranium and substantially all of themetal impurities, recovering the uranium contained in the electrolyzedsolution, scrubbing the mercury of the cathode with a wash solution toremove therefrom the contained trace of uranium, and then recovering theuranium from the wash solution. Y

14. The process comprising calcining uranous oxalate in a stream of dryair at a temperature of about 500 C., whereby the uranous oxalate isconverted to uranosic oxide and reaction gases are evolved carrying afraction of the uranium, recovering substantially all of the uranosicoxide produced incident to calcination, subjecting the last-mentionedreaction gases to electrostatic precipitation in order to reclaimsubstantially all of the fraction of uranium carried thereby, wherebythe last-mentioned reaction gases after being subjected to electrostaticprecipitation carry a trace of uranium, reacting the uranosic oxide andcarbon tetrachloride in the vapor phase at a temperature of about 475C., whereby the uranosic oxide is converted to uranium tetrachloride andreaction gases are evolved carrying a fraction of the uranium,recovering substantially all of the uranium tetrachloride producedincident to the reaction, subjecting the lastmentioned reaction gases toelectrostatic precipitation in order to reclaim substantially all of thefraction of uranium carried thereby, whereby the last-mentioned reactiongases after being subjected to electrostatic precipitation carry a traceof uranium, combining the rstmentioned reaction gases after they havebeen subjected to electrostatic precipitation and the last-mentionedreaction gases after they have been subjected to elecrostaticprecipitation, and then scrubbing the combined reaction gases with asuitable liquid solvent in order to salvage the trace of uranium carriedthereby.

15. The process comprising calcining uranous oxalate in a stream of dryair at a temperature of about 500 C., whereby the uranous oxalate isconverted to uranosic oxide and reaction gases are evolved carrying afraction of the uranium, recovering substantially all of the uranosicoxide produced incident to calcination, subjecting the reaction gases toelectrostatic precipitation in order to reclaim substantially all of thefraction of uranium carried thereby, whereby the reaction gases afterbeing subjected to electrostatic precipitation carry a trace of uranium,and then scrubbing the reaction gases with a suitable liquid solvent inorder to salvage the trace of uranium carried thereby.

16. The process comprising reacting uranosic oxide and carbontetrachloride in the vapor phase at a temperature of about 475 C.,whereby the uranosic oxide is converted to uranium tetrachloride andreaction gases are evolved carryingva fraction of the uranium,recovering substantially all of the uranium tetrachloride producedincident to the reaction, subjecting the reaction gases to electrostaticprecipitation in order to reclaim substantially all of the fraction ofuranium carried thereby, whereby the Vreaction gases after beingsubjected to electrostatic precipitation carry a trace of uranium, andthen scrubbing the reaction gases with a suitable liquid solvent inorder to salvage the trace of uranium carried thereby.

17. The process of reclaiming uranium from a hydrochloric acid solutioncontaining UO2++ ion comprising subjecting the solution to a reducingtreatment in order to reduce UO2++ ion to U++++ ion in which treatmentthe solution is heated to above about C., thereafter cooling thesolution to below about 20 C. in order to prevent substantialre-oxidation of U++++ ion back to UO2++ ion, and then reacting thesolution with a stoichiometric excess of oxalic acid in order toprecipitate uranium as uranous oxalate.

References Cited in the le of this patent UNITED STATES PATENTS1,050,796 Bleecker Jan. 21, 1913 1,054,102 Fischer Feb. 25, 19131,210,714 Seil Jan. 2, 1917 1,224,014 Parsons Apr. 24, 1917 1,286,400Pellegrin Dec. 3, 1918 1,526,943 Thews Feb. 17, 1925 1,900,996 PalmaerMar. 14, 1933 2,176,609 McCormack Oct. 17, 1939 OTHER REFERENCES Friend:Textbook of Inorganic Chemistry, vol. 7, part 3, pages 287, 289, 290,307 (1926). Pub. by Charles Griin and Co., London.

Babor et al.: General College Chemistry, 2nd. edition, (1940), page 317.Pub. by Thos. Y. Crowell Co., N. Y.

1. THE PROCESS OF RECLAIMING URANIUM VALUES FROM THE PARTS OF A CALUTRONUPON WHICH IT IS DEPOSITED COMPRISING WASHING THE PARTS MENTIONED WITH ASOLVENT FOR THE URANIUM, WHEREBY URANYL IONS AND THE IONS OF METALIMPURITIES OF A CLASS THAT FORMS SOLUBE OXLTES IN ACID SOLUTION AREINTRODUCED IN THE WASH SOLUTION, SUBJECTING THE WASH SOLUTION TO AREDUCING TREATMENT TO CONVERT THE URANYL INTO URANOUS IONS IN THESOLUTION, THEN TREATING THE SOLUTION WITH A STOICHIOMETRIC EXCESS OFOXALIC AND HYDROCHLORIC ACIDS TO PRECIPITATE THE URANIUM AS URANOUSOXALATE AWAY FROM METAL IMPURITIES IN THE SOLUTION FORMING A SLURRYWHICH IS ABOUT 1 TO 3 N IN HYDROCHLORIC ACID, SEPARATION THE WET URANOUSOXALATE PRECIPITATE FROM THE SOLUTION, CONTACTION THE WET URANOUSOXALATE PRECIPITATE WITH A SUITABLE LIQUID DRYING AGENT, WHEREBY THE WETURANOUS OXALATE PRECIPITATE IS DRIED, AND THEN CALCINING THE DRIEDURANOUS OXALATE PRECIPITATE TO PRODUCE A URANIUM OXIDE.